refactor: biome's spawn-list parsers live in biome.rs

parse_entries, parse_costs and SpawnCost read the biome JSON's
natural_mob_spawns and build biome::SpawnEntry; biome.rs reached into
mobs::spawn_selection for them, one of the edges that keep the client lib
in a single cycle. They move to biome.rs and spawn_selection re-exports
them. No behaviour change.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/horizon-client/src/biome.rs

@@ -20,12 +20,68 @@ pub struct SpawnEntry {
     /// A `ConstantInt` count (sampling draws nothing).
     pub constant: bool,
 }
+/// A `natural_mob_spawns` / `spawn_overrides` entry list.
+pub fn parse_entries(list: &Value) -> Vec<SpawnEntry> {
+    list.as_array()
+        .into_iter()
+        .flatten()
+        .filter_map(|e| {
+            let count = &e["count"];
+            let (min, max, constant) = match count {
+                Value::Number(n) => {
+                    let n = n.as_u64().unwrap_or(1) as u32;
+                    (n, n, true)
+                }
+                c if c["type"].as_str() == Some("minecraft:constant") => {
+                    let n = c["value"].as_u64().unwrap_or(1) as u32;
+                    (n, n, true)
+                }
+                c => (
+                    c["min_inclusive"].as_u64().unwrap_or(1) as u32,
+                    c["max_inclusive"].as_u64().unwrap_or(1) as u32,
+                    false,
+                ),
+            };
+            Some(SpawnEntry {
+                entity: e["type"].as_str()?.to_owned(),
+                weight: e["weight"].as_u64().unwrap_or(1) as u32,
+                min,
+                max,
+                constant,
+            })
+        })
+        .collect()
+}
+/// `MobSpawnSettings.MobSpawnCost`.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct SpawnCost {
+    pub energy_budget: f64,
+    pub charge: f64,
+}
+/// The `spawn_costs` of a `natural_mob_spawns` value.
+pub fn parse_costs(costs: &Value) -> HashMap<String, SpawnCost> {
+    costs
+        .as_object()
+        .into_iter()
+        .flatten()
+        .map(|(k, c)| {
+            (
+                k.clone(),
+                SpawnCost {
+                    energy_budget: c["energy_budget"].as_f64().unwrap_or(0.0),
+                    charge: c["charge"].as_f64().unwrap_or(0.0),
+                },
+            )
+        })
+        .collect()
+}
+
 #[derive(Clone, Debug)]
 pub struct BiomeInfo {
     /// `natural_mob_spawns` by category (creature, monster, ...).
     pub spawns: HashMap<String, Vec<SpawnEntry>>,
     /// `natural_mob_spawns` spawn costs by entity type.
-    pub spawn_costs: HashMap<String, crate::mobs::spawn_selection::SpawnCost>,
+    pub spawn_costs: HashMap<String, SpawnCost>,
     /// The `gameplay/creature_world_gen_spawn_probability` attribute.
     pub creature_probability: f32,
     /// The `gameplay/increased_fire_burnout` attribute (jungles, swamps, peaks,
@@ -143,12 +199,12 @@ impl Biomes {
             };
             let categories = &natural["spawns_by_category"];
             for (category, entries) in categories.as_object().into_iter().flatten() {
-                let list = crate::mobs::spawn_selection::parse_entries(entries);
+                let list = parse_entries(entries);
                 spawns.insert(category.clone(), list);
             }
             list.push(BiomeInfo {
                 spawns,
-                spawn_costs: crate::mobs::spawn_selection::parse_costs(&natural["spawn_costs"]),
+                spawn_costs: parse_costs(&natural["spawn_costs"]),
                 creature_probability:
                     attributes["minecraft:gameplay/creature_world_gen_spawn_probability"]
                         .as_f64()

crates/horizon-client/src/mobs/spawn_selection.rs

@@ -23,61 +23,7 @@ use horizon_core::{
 use serde_json::Value;
 use std::{collections::HashMap, fs, path::Path};
 
-/// A `natural_mob_spawns` / `spawn_overrides` entry list.
-pub fn parse_entries(list: &Value) -> Vec<SpawnEntry> {
-    list.as_array()
-        .into_iter()
-        .flatten()
-        .filter_map(|e| {
-            let count = &e["count"];
-            let (min, max, constant) = match count {
-                Value::Number(n) => {
-                    let n = n.as_u64().unwrap_or(1) as u32;
-                    (n, n, true)
-                }
-                c if c["type"].as_str() == Some("minecraft:constant") => {
-                    let n = c["value"].as_u64().unwrap_or(1) as u32;
-                    (n, n, true)
-                }
-                c => (
-                    c["min_inclusive"].as_u64().unwrap_or(1) as u32,
-                    c["max_inclusive"].as_u64().unwrap_or(1) as u32,
-                    false,
-                ),
-            };
-            Some(SpawnEntry {
-                entity: e["type"].as_str()?.to_owned(),
-                weight: e["weight"].as_u64().unwrap_or(1) as u32,
-                min,
-                max,
-                constant,
-            })
-        })
-        .collect()
-}
-/// `MobSpawnSettings.MobSpawnCost`.
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub struct SpawnCost {
-    pub energy_budget: f64,
-    pub charge: f64,
-}
-/// The `spawn_costs` of a `natural_mob_spawns` value.
-pub fn parse_costs(costs: &Value) -> HashMap<String, SpawnCost> {
-    costs
-        .as_object()
-        .into_iter()
-        .flatten()
-        .map(|(k, c)| {
-            (
-                k.clone(),
-                SpawnCost {
-                    energy_budget: c["energy_budget"].as_f64().unwrap_or(0.0),
-                    charge: c["charge"].as_f64().unwrap_or(0.0),
-                },
-            )
-        })
-        .collect()
-}
+pub use crate::biome::{SpawnCost, parse_costs, parse_entries};
 
 /// `MobCategory`.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]

tools/test_natural_spawn_parity.py

@@ -552,6 +552,7 @@ def main():
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaNaturalSpawnOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/probe/natural_spawn_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_selection.rs',
+               lab.ROOT / 'crates/horizon-client/src/biome.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_rules.rs']
     tested = base.source_hashes(sources)
     inputs = build / 'inputs.txt'

tools/test_spawner_parity.py

@@ -233,6 +233,7 @@ def main():
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/probe/natural_spawn_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawner.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_selection.rs',
+               lab.ROOT / 'crates/horizon-client/src/biome.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_rules.rs']
     tested = base.source_hashes(sources)
     inputs = build / 'inputs.txt'

tools/test_trial_spawner_parity.py

@@ -198,6 +198,7 @@ def main():
                lab.ROOT / 'crates/horizon-client/src/mobs/trial_spawner.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawner.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_selection.rs',
+               lab.ROOT / 'crates/horizon-client/src/biome.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_rules.rs']
     tested = base.source_hashes(sources)
     inputs = build / 'inputs.txt'